2nd Generation CNC Mill

TWS-1850

a 3rd Generation CNC mill...

It's been just over a year since the "NexMill-15" was completed, and well over 3 years since the original 3 axis mill was built, so I figured the time was right to start yet another machine to do my bidding.

If this is your first time to theworkshop.ca, or you landed here in search of how to build a 3 Axis CNC mill, you may want to browse the links below to get a sense of the evolution that has precipitated so far...

3-Axis Mill - Part1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17

Nex-Mill15 (CNC) Part1 , 2, 3, 4, 5, 6, 7,

Assuming that your either familiar with the above or don't have the time, interest or energy to wade through so much detail, lets get started.

The rack pictured to the right came courtesy of www.pc4kids.ca a local non-profit computer refurb center...

I had the pick of several units and this was the one I felt best met my needs.

Given that the NexMill-15 has worked out so well being built on a half rack platform, it only seemed logical that going with a full-rack would be twice as good.

The rack was semi-disassembled and re-oriented to lay flat on it's back. Numerous holes were drilled through the side panels and 1/4" #20 bolts, washers and nuts used to fasten the framing and sides more securely.

A sub-floor of sorts was also fastened into place and used to accommodate 4" solid rubber castors for ease of movement. The NexMill is similarly out-fitted and this has proven to be a feature that I appreciate given that the shop is re-configured regularly to free-up floor space as required.

The image to the left is of some misc parts that will be incorporated into this project, primarily the smaller box & rails sitting on the floor.

The larger assembly will be scavenged for the 1/4" aluminum plate for various fixtures.

To the right is my current stash of unipolar stepper motors.

Given that this mill will be over three times the size of the previous unit, I'm hoping to implement a total of 7 (seven) steppers rather than the typical 3 (one per axis).

The Z axis or plunge will only have one stepper, while the 18" X axis will have 2 (two) steppers, one on either end of the lead screw (one driving Clockwise, with the other driving counter clockwise in step).

The 50" Y axis will have 2 lead screws arranged similar to the X axis, with a total of 4 steppers.

The idea of moving beyond steppers to a closed loop servo drive system simply isn't an option at his point, especially given that I have all the materials in-stock from the steppers through to the driver components.

On the floor (pictured above) are 4 industrial drawer slides, initially I picked up a pair from Princess Auto for approx $20 ea, after playing with them for a day or two, I concluded that I really needed 2 per side to provide the support necessary. Unfortunately the second pair doubled in price as the first were on special.

After much putzing about with the slide rails I decided to dis-assemble a set to see if I could gain an additional 9 or 10 inches of travel over the stock 42".

Each assembly required 4 retaining tabs to be cut out, and the bearing races were cut back to 3/5ths their original length.

I can appreciate that this may seem meaningless if you've never worked with slide rails such as these, but the end result is close to 54" of travel, a net gain of 12".

A diversion of sorts...

And things sat like this for a couple of weeks, as I was simply too over-come by inertia to deal with mess that had over-taken the original milling station.

I think the worst of it was seeing the actual mill sitting under the bench on the floor in a state of neglect.

In an effort to regain some momentum, I opted to clean up the bench and remove it entirely to make room for the Gen-3 as it is perpetually in the way as I work on other projects.

As I'm keen on rolling benches and already have 3 others that allow a flexible workflow between the machine shop and the foundry, it seemed like the logical choice.

This is a discarded bar-b-q rack that will form the base for the task at hand.

A 3/4" MDF table top is bolted into place through the light steel framing with 1/4" #20 bolts

The sides are stiffened with more MDF.

The base (near the floor) is flipped over to form a "lipped" shelf, and the original framing that the actual BBQ and controls were mounted to is also inverted with an MDF sheet to add a shelf half way up.

The MDF is sealed with a couple coats of clear lacquer to extend it's life given the common occurrence of spilled drinks, oily parts and whatever else typically erodes MDF.

Remarkably everything fit onto the cart that relates to the Gen-3 Mill project and the bench has been taken down.

Back on track...

If I didn't have over $100 bucks tied-up in these slide rails, I'd have thrown them out at this point.

Or at least put them aside... What isn't readily apparent with such units is the gross amount of space that they require to move the full length of their travel.

Incredibly it took 3 full days of positioning, measuring and re-positioning to accomplish 50" of "Supported" travel over a 96" span of space.

The MDF panel pictured here will be one of the sides of the mill.

Once I had determined the best positioning and reference points the second side took only an hour and a half to mark.

I dug out this old portable drill stand (note that I'm hesitant to call it a "Drill-Press").

The point of using this rig was to ensure that the holes required were as straight as possible, given that the 8 ft length of MDF is a bit unwieldy to handle and I didn't want skewed holes positioning the MDF crooked on the level base.

The sides are held in place by 6 carriage bolts through the metal framing, and will have 8 more bolts for the rails per side.

The table top is screwed into place with 2" MDF every 4" into 1/8" pilot holes.

The top was carefully cut on a panel saw to provide a 1/2" overhang that will aid in aligning the rails to parallel on each side.

The assembly is pictured here with a couple coats of Hi-Build primer just to seal the MDF.

The primer will be sanded smooth and painted the same shade of dark blue as the other CNC Mills.

I'd like to also add some minor graphics, but haven't decided on exactly what quite yet...

While I ponder the options of graphics and the like, I thought I would move forward with some hardware that I knew would be required.

This is the "flat" just machined on the NexMill-15 for the stepper mounting hardware that will be cast in an Aluminum alloy.

As always the parts are drafted to scale in Corel Draw, exported as a DXF, converted to GCode and fired off on the mill.

The pieces from the "Flat" are carefully cut-out on a band-saw and hot-glued together.

These parts are over-sized to allow for an 18 thou per inch shrinkage factor once cast.

Each piece is carefully sanded and cleaned-up while still as a foam piece to minimize the more laborious task when metal.

Although I only needed 4 ( four) pieces for the Y-Axis stepper mounts, I opted to cast 2 spares just incase.

As it turns out that was a prudent move as one mold didn't completely fill, and I broke a 2nd part while cutting away the feeders.

To the left are the cleaned parts ready for test fitting once the table is painted and the rails are mounted.

This project will likely extend through the summer with a conservative "Go-Live" by mid to late Aug.

As an aside the purpose of this machine is twofold, a) to machine larger part flats and patterns for casting, and b) as a "Blade Carver" for windmills.

I thought it was neat to try and work in the machining envelope of 18" x 50" named TWS-1850 as a tie-back to the fact that oil was first drilled by Edwin Drake in the 1850's in the U.S.A. and the machine will be used for machining wind-mill blades... Get it??? 1850, oil, windmill blades?

...never-mind

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